Bash Shell Script – How to Pass Array

arraybashshellshell-script

How do I pass an array as a variable from a first bash shell script to a second script.

first.sh

#!/bin/bash
AR=('foo' 'bar' 'baz' 'bat')
sh second.sh "$AR" # foo
sh second.sh "${AR[@]}" # foo

second.sh

#!/bin/bash
ARR=$1
echo ${ARR[@]}

In both cases, the result is foo. But the result I want is foo bar baz bat.

What am I doing wrong and how do I fix it?

Best Answer

AFAIK, you can't. You have to serialize it and deserialize it, e.g. via the argument array:

first

#!/bin/bash
ar=('foo' 'bar' 'baz' 'bat')
second "${ar[@]}" #this is equivalent to: second foo bar baz bat

second

#!/bin/bash
arr=( "$@" )
printf ' ->%s\n' "${arr[@]}"
<<PRINTS
   -> foo
   -> bar
   -> baz
   -> bat
PRINTS

A little bit of advice:

reserve all caps for exported variables
unless you have a very good specific reason for not doing so "${someArray[@]}" should always be double quoted; this formula behaves exactly like 'array item 0' 'array item 1' 'aray item 2' 'etc.' (assuming someArray=( 'array item 0' 'aray item 1' 'aray item 2' 'etc.' ) )

Related Solutions

Bash eval array variable name

The simplest form for parameter expansion is: ${parameter}.
Using braces in confused case is better way.

Considering of possibilities of being included spaces in array of "myvarA", I think this would be the answer.

#!/bin/bash -x
myvarA=( "variable  A1" "variable  A2" )
varname="A"

eval varAlias=( '"${myvar'${varname}'[@]}"' )
eval varAlias=( \"\${myvar${varname}[@]}\" ) # both works
for varItem in "${varAlias[@]}" # double quote and `@' is needed
do
    echo "$varItem"
done

Bash – Accessing Array Index Variable in Shell Script Loop

You can do this using List of array keys. From the bash man page:

${!name[@]}
${!name[*]}

List of array keys. If name is an array variable, expands to the list of array indices (keys) assigned in name. If name is not an array, expands to 0 if name is set and null otherwise. When @ is used and the expansion appears within double quotes, each key expands to a separate word.

For your example:

#!/bin/bash
AR=('foo' 'bar' 'baz' 'bat')
for i in "${!AR[@]}"; do
  printf '${AR[%s]}=%s\n' "$i" "${AR[i]}"
done

This results in:

${AR[0]}=foo
${AR[1]}=bar
${AR[2]}=baz
${AR[3]}=bat

Note that this also work for non-successive indexes:

#!/bin/bash
AR=([3]='foo' [5]='bar' [25]='baz' [7]='bat')
for i in "${!AR[@]}"; do
  printf '${AR[%s]}=%s\n' "$i" "${AR[i]}"
done

This results in:

${AR[3]}=foo
${AR[5]}=bar
${AR[7]}=bat
${AR[25]}=baz

Best Answer

Related Solutions

Bash eval array variable name

Bash – Accessing Array Index Variable in Shell Script Loop

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